Radiant Heating Assembly with Liner Tube and Temperature Limiting Device

ABSTRACT

A radiant heating assembly includes a fuel valve, a blower, a controller configured to control the fuel valve and the blower, and a heat exchanger or burner tube configured to limit external surface temperature through the use of a liner tube and a temperature limiting device. The liner tube can be installed internally into the walls of a heat exchanger or burner tube to decrease the surface temperature of the heat exchanger.

RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/361,172, filed on Jul. 12, 2016, the entire contents of which are hereby incorporated by reference.

BACKGROUND 1. Field of the Invention

The subject invention generally relates to a radiant heating assembly utilizing a liner tube and an outer heating tube arrangement.

2. Description of the Related Art

Radiant heaters are widely utilized for a variety of heating purposes. One common type of radiant heater is a radiant tube heater including a burner and a heat tube extending from the burner. In the radiant tube heater, a gas valve provides gas into the burner while a blower motor provides air to the burner. The gas and the air are typically mixed and ignited in the burner. A flame and/or heated exhaust may pass from the burner to the heat tube such that the radiant tube heater emits radiant heat.

The radiant tube heater may be installed at various different heights above a floor or subjected to a wide variety of environmental conditions. Additionally, users of the radiant tube heater may desire a balanced distribution of heat across a length of the heat tube by selectively increasing blower speed to force the air quickly across the length of the heat tube. Alternatively, users may desire to operate the radiant tube heater in a more thermally efficient manner by selectively reducing input of air and gas into the burner.

Normal operating exterior surface temperatures of the radiant tube heater may be more than 1000° F. In some applications, it is necessary to reduce the external surface temperature of radiant tube heaters for safety or other purposes. In these applications, modification in design of the radiant tube heater must be made to reduce the exterior surface temperature and the radiant tube heater may require some manner of ensuring that exterior surface temperatures do not exceed a predetermined temperature.

Attempts have been made in developing tubes for radiant tube heaters to reduce the exterior surface temperature. Different materials have been used with varying thermal properties. Modulation of fuel flow and blower speed to reduce heat output are alternative solutions that have been used to reduce exterior surface temperature. Although such solutions have been used to decrease exterior surface temperature, such solutions often require changes in heat output.

Attempts have also been made in monitoring exterior surface temperature to ensure that the temperature does not exceed a desired value. Thermocouples have been added to radiant tube heaters. In some cases wires are wrapped around the radiant tube heater along a length of the radiant tube heater and short out when the exterior surface temperature exceeds a predetermined temperature. Although such systems ensure exterior surface temperatures do not exceed a predetermined temperature, they often require an additional power source. In the case of the wire system, wires will need to be replaced and inspected regularly to ensure continued operation.

Accordingly, there remains an opportunity to provide a radiant tube heater that beneficially addresses the deficiencies set forth above. In other words, there remains an opportunity to provide a radiant tube heater which decreases the surface temperature of the radiant tube heater during operation. Specifically, there remains an opportunity to provide a radiant tube heater including a liner tube and spacing elements to engage with the liner tube and an outer tube to reduce surface temperature. Further, there remains an opportunity to provide a radiant tube heater which limits the external surface temperature of the radiant tube heater during operation. Specifically, there remains an opportunity to provide a radiant tube heater including a temperature limiting device requiring a single power source for operation of the radiant tube heater and the temperature limiting device.

SUMMARY

The present invention includes a burner for receiving air and fuel for combustion and emitting heated exhaust or wash air. The present invention further includes an elongated heat exchanger in communication with the burner defining a first end and a second end and a length between the first and second ends. The elongated heat exchanger includes an outer tube disposed along at least a portion of the length and defines an interior. The elongated heat exchanger further includes a liner tube disposed within the interior along at least a portion of the length and defines an inner chamber for receiving the heated exhaust or wash air. The elongated heat exchanger additionally includes at least one spacing element disposed within the interior between the liner tube and the outer tube and engaging both the liner tube and the outer tube to space the liner tube from the outer tube along at least a portion of the length.

One embodiment of a radiant heating assembly includes a burner for receiving air and fuel for combustion and emitting heated exhaust or wash air. The radiant heating assembly further includes an elongated heat exchanger in communication with the burner defining a first end and a second end and a length between the first and second ends. The radiant heating assembly additionally includes a controller configured to control the amount of the air and the fuel provided to the burner. A temperature limiting device is coupled to the elongated heat exchanger comprising. The temperature limiting device includes a tube having an exterior surface and an interior surface. The interior surface defines a tube interior in fluid communication with the elongated heat exchanger, and with the tube coupled to the elongated heat exchanger along the length. The temperature limiting device further includes a temperature limit switch coupled to the exterior surface of the tube. The temperature limit switch is operable between a first state when temperature of the exterior surface is at or below a predetermined temperature and a second state, different from the first state, when the temperature of the exterior surface is above the predetermined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a radiant heating assembly including an elongated heat exchanger and a housing;

FIG. 2 is a perspective view, partially in phantom, of the radiant heating assembly of FIG. 1 including a burner, a fuel valve for providing fuel to the burner, a blower for providing air to the burner, and a controller configured to control the air and the fuel provided to the burner;

FIG. 3A is a perspective view of a radiant heating assembly of the present invention including a housing and an elongated heat exchanger or burner tube with an outer tube and a liner tube of the present invention useable with the assembly of FIG. 2;

FIG. 3B is an alternative perspective view of a radiant heating assembly of the present invention including a housing and an elongated heat exchanger or burner tube with an outer tube and a liner tube of the present invention useable with the assembly of FIG. 2;

FIG. 4A is a cross-sectional view of one embodiment of the heat exchanger with the liner tube and the outer tube, and an array of support fins collectively forming spacing elements for spacing the liner tube from the outer tube.

FIG. 4B is a cross-sectional view of another embodiment of the heat exchanger with the liner tube and the outer tube, and an array of dimples forming spacing elements for spacing the liner tube from the outer tube.

FIG. 4C is a cross-sectional view of another embodiment of the heat exchanger with the liner tube and the outer tube, and an array of depressions integrated with the outer tube forming spacing elements for spacing the liner tube from the outer tube and the liner tube defining indents for receiving the spacing element.

FIG. 5A is a perspective view of one embodiment of the liner tube with spacing elements equiangularly disposed about the liner tube.

FIG. 5B is a perspective view of another embodiment of the liner tube with spacing elements randomly disposed about the liner tube.

FIG. 5C is a perspective view of still another embodiment of the liner tube with spacing elements disposed in a spiral about the liner tube.

FIGS. 6, 7, and 8 are perspective views of an alternative embodiment of a radiant heating assembly including a housing and an elongated heat exchanger or burner tube in a U-shape.

FIG. 9A is a detailed drawing of a heat exchanger or burner tube having the liner tube of the present invention used with the device of FIGS. 6-8.

FIG. 9B is a cross-sectional view of the embodiment shown in FIG. 9A with the liner tube and outer tube in a U-shape.

FIG. 10 is a perspective view of a temperature limiting device.

FIG. 11A is a perspective view of the temperature limiting device in a first state.

FIG. 11B is a perspective view of the temperature limiting device in a second state.

FIG. 12A is a perspective view of the temperature limiting device at a first distance from the burner.

FIG. 12B is a perspective view of the temperature limiting device at a second distance from the burner.

DETAILED DESCRIPTION

Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a radiant heating assembly is generally shown at 20. As shown in FIG. 1, the radiant heating assembly 20 is typically suspended above an area to heat the area. The radiant heating assembly 20 may be installed in the interior or the exterior of any type of building or structure, such as a restaurant, factory, warehouse, arena, etc. Alternatively, the radiant heating assembly 20 may be independently suspended above any area such as a patio, and the like.

The radiant heating assembly 20 may include a housing 22 for accommodating various components of the radiant heating assembly 20. The housing 22 is typically formed of sheet metal but may be formed of any type of material without departing from the nature of the present invention. Furthermore, the housing 22 may have any suitable configuration for accommodating various components of the radiant heating assembly 20.

With reference to FIG. 2, the radiant heating assembly 20 includes a burner 24 for receiving air and fuel for combustion. The burner 24 typically has an inlet 26 for receiving the air and fuel. The air and fuel are typically mixed and ignited in the burner 24. However, it is to be appreciated that the air and fuel may be mixed before being received by the burner 24 according to any suitable method. The burner 24 typically combusts the air and fuel into exhaust. This exhaust is commonly referred to as “wash air”. The burner 24 may include an outlet 28 for emitting exhaust generated by combustion of the air and fuel. Optionally, the radiant heating assembly 20 may include a plurality of burners 24. The burner 24 may have a venturi configuration but alternatively may have other configurations without departing from the nature of the present invention. The burner 24 is typically disposed at least partially within the housing 22.

The radiant heating assembly 20 includes an elongated heat exchanger or burner tube 30 in communication with the burner 24. The elongated heat exchanger 30 typically has an inlet 32 for receiving the exhaust emitted by the outlet 28 of the burner 24. The burner 24 may be positioned adjacent the inlet 32 of the elongated heat exchanger 30. The exhaust emitted by the outlet 28 of the burner 24 passes through and heats the elongated heat exchanger 30 such that the elongated heat exchanger 30 emits radiant heat. The elongated heat exchanger or burner tube 30 may be coupled to the housing 22 at one end. The elongated heat exchanger 30 may include a vent cap at another end to vent the exhaust passing through the elongated heat exchanger 30. Generally, the elongated heat exchanger 30 is mounted below a reflector 34 covering a significant portion of a length of the elongated heat exchanger 30. The reflector 34 directs radiant heat in a directional path towards the area to be heated to optimize the pattern of radiant heat emitted by the elongated heat exchanger 30.

The elongated heat exchanger or burner tube 30 may have various lengths and shapes. Typically, the elongated heat exchanger 30 has a circular cross-section. However, the elongated heat exchanger 30 may have other cross-sections such as a rectangular cross-section, and the like. The elongated heat exchanger 30 may extend in any suitable path, such as a straight path, an L-shaped path, a U-shaped path, and the like. Additionally, the radiant heating assembly 20 may include a plurality of elongated heat exchangers 30 for receiving exhaust emitted by one or a plurality of burners 24.

The radiant heating assembly 20 includes a fuel valve 36 for providing the fuel to the burner 24. The fuel valve 36 may provide fuel directly to the inlet 26 of the burner 24. Alternatively, the fuel valve 36 may provide the fuel indirectly to the burner 24. For example, the fuel valve 36 may pass the fuel through a pre-mixing chamber before entering the burner 24. Typically, the fuel valve 36 is coupled to a fuel source 40 which provides fuel to the fuel valve 36. The fuel may be natural gas, although any suitable fuel, such as propane, may be received by the fuel valve 36. The fuel valve 36 may be disposed within the housing 22.

The fuel valve 36 may be configured to provide the fuel according to a modulating operation, but may also be supplied without modulating operation. With respect to the fuel valve 36, the term “modulating,” is meant generally to describe operating the fuel valve 36 according to any given one of a plurality of fuel input rates defined within a predetermined range of fuel input rates. In the modulating operation, the fuel valve 36 may provide the fuel to the burner 24 according to one of the plurality of fuel input rates. It is to be appreciated that the fuel input rate may correspond to any suitable unit of measurement. The fuel valve 36 is generally capable of allowing from 0% to 100% of the fuel provided to the fuel valve 36 to pass to the burner 24. Said differently, the fuel valve 36 is capable of opening between 0% and 100% to provide various amounts of the fuel to the burner 24.

The radiant heating assembly 20 includes a blower 42 for providing the air to the burner 24. The blower 42 may receive the air and provide the air directly to the inlet 26 of the burner 24. Alternatively, the blower 42 may provide the air indirectly to the burner 24. For example, the blower 42 may pass the air through a pre-mixing chamber before entering the burner 24. Typically, the blower 42 receives air from an air source 46 such as ambient air. In particular, the blower 42 may draw the air through an aperture 48 defined in the housing 22 before providing the air to the burner 24. The blower 42 may be disposed within the housing 22 and in fluid communication with the elongated heat exchanger 30 for forcing the exhaust through the elongated heat exchanger 30.

In one embodiment, the blower 42 may force the air through the burner 24 and the exhaust through the elongated heat exchanger 30 by expelling the air away from the blower 42. Alternatively, the blower 42 may force the air through the burner 24 and the exhaust through the elongated heat exchanger 30 by pulling the air towards the blower 42.

As with the fuel valve 36, the blower 42 may be configured to provide the air according to a modulating operation, or may be supplied with no modulation whatsoever. With respect to the blower 42, the term “modulating,” is meant generally to describe operating the blower 42 according to any given one of a plurality of blower input rates defined within a predetermined range of blower input rates. The blower 42 typically includes a variable speed motor capable of providing the air at various rates. More specifically, the variable speed motor may be an electrically commutated motor or a permanent split capacitor motor. The blower 42 is generally capable of operating between 0 and 10,000 RPM. However, it is to be appreciated that the blower 42 may operate in any other suitable range. In the modulating operation, the blower 42 may provide the air to the burner 24 according to one of the plurality of blower input rates, as will be described below. The blower input rate may correspond to any suitable unit of measurement. For example, the blower input rate may correspond to a pressure differential measured at one or more locations within the blower 42, the burner 24, and the elongated heat exchanger 30, and the like. Specifically, the radiant heating assembly 20 may include a pressure sensor for measuring the pressure differential and for providing a signal corresponding to the pressure differential measured.

As shown in FIG. 2, the radiant heating assembly 20 includes a controller 50 configured to control the amount of the air and the fuel provided to the burner 24 by modulating at least one of the fuel valve 36 and the blower 42. The controller 50 may include a processing unit, such as a microcontroller for receiving inputs and processing and executing commands. Furthermore, the controller 50 may include logic, such as PID logic, and memory for monitoring information on past on/off heating cycles and optimizing on/off heating cycles based on the monitored information for increasing efficiency of the radiant heating assembly 20. The controller 50 may be disposed within the housing 22 and electrically connected to the fuel valve 36 and the blower 42. The controller 50 is in electrical communication with a power source (not shown). However, electrical connections between the controller 50, the fuel valve 36, and the blower 42 are generally not shown in the figures for simplicity in illustration.

The radiant heating assembly 20 may include an ignition controller 52. Typically, the ignition controller 52 is operatively connected between the burner 24 and the controller 50. Furthermore, an ignitor 54 may be disposed within or adjacent to the burner 24 for providing a flame for igniting the air and the fuel within the burner 24. The ignitor 54 may be controlled by the ignition controller 52. In addition, a flame sensor may be disposed adjacent the burner 24 for monitoring the flame within the burner 24. The ignition controller 52 regulates the flame provided by the ignitor 54 according to signals provided by the flame sensor. The ignition controller 52 is typically mounted in the housing 22. The ignition controller 52 may be configured to provide ignition sequencing and safety lock-out operations for the radiant heating assembly 20.

In some instances, the controller 50 may modulate the fuel valve 36 independent of the blower 42. That is, the controller 50 may provide a fuel control signal to the fuel valve 36 before or after providing a blower control signal to the blower 42. Similarly, the controller 50 may vary the fuel control signal before or after varying the blower control signal.

Alternatively, the controller 50 may simultaneously modulate the fuel valve 36 and the blower 42. Specifically, the controller 50 may provide the fuel control signal to the fuel valve 36 simultaneously while providing the blower control signal to the blower 42. Moreover, the controller 50 may vary the fuel control signal simultaneously while varying the blower control signal.

With reference to FIG. 1, the elongated heat exchanger 30 defines a first end 56 coupled to the housing 22 and a second end 58 extending from the first end 56. The elongated heat exchanger 30 further defines a length between the first 56 and second 58 ends.

As shown in FIGS. 3A and 3B, the elongated heat exchanger 30 further includes an outer tube 60 disposed along at least a portion of the length. The outer tube 60 defines an interior 62 for receiving the exhaust. The elongated heat exchanger 30 additionally includes a liner tube 64 disposed within the interior 62 along at least a portion of the length. The liner tube 64 defines an inner chamber 66 in fluid communication with the interior 62. The elongated heat exchanger 30 further includes at least one spacing element 68 disposed within the interior 62 between the liner tube 64 and the outer 60 tube. The spacing elements 68 engage both the liner tube 64 and the outer 60 tube to space the liner tube 64 from the outer tube 60 along at least a portion of the length.

In one embodiment illustrated in FIG. 4A, each spacing elements 68 is a support fin 70 disposed along at least a partial length of the elongated heat exchanger 30 and coupled to one of the liner tube 64 and the outer tube 60. In another embodiment illustrated in FIG. 4B, the spacing element 68 is a dimple 72. The dimple 72 may have a convex shape. In one embodiment shown in FIG. 4C including the dimple 72, the dimple 72 is a depression 73 formed from one of the liner tube 64 and the outer tube 60, such that the spacing element 68 is integrated with one of the liner tube 64 and the outer tube 60. In still other embodiments, it is to be appreciated that the spacing elements 68 may have any physical configuration for engaging both the liner tube 64 and outer tube 60 to space the liner tube 64 from the outer tube 60 without departing from the nature of the invention.

In the embodiments illustrated in FIGS. 4A, 4B, 4C, the elongated heat exchanger 30 includes three spacing elements 68. However, it is to be appreciated that the elongated heat exchanger 30 may include any number of spacing elements 68 without departing from the nature of the invention.

In one embodiment illustrated in FIGS. 4A, 4B, 4C, and 5A, the spacing elements 68 define angles between adjacent spacing elements 68 with the axis A being a vertex for each angle. The spacing elements 68 are radially disposed about the axis A and coupled to the liner tube 64, such that the angles created by adjacent spacing elements 68 are equal. Said differently, the spacing elements 68 are radially disposed about the liner tube 64 such that spaces between consecutive spacing elements 68 are equal.

In another embodiment illustrated in FIG. 5B, the spacing elements 68 are radially disposed about the axis A and coupled to the liner tube 64, such that the angles created by adjacent spacing elements 68 are randomized. In this embodiment, the angles may be equal or unequal. Said differently, the spacing elements 68 are radially disposed about the liner tube 64 such that spaces between consecutive spacing elements 68 may be equal or unequal.

In still another embodiment illustrated in FIG. 5C, the spacing elements 68 are radially disposed about the axis A and coupled to the liner tube 64, such that the spacing elements 68 form at least one spiral about the axis A. It is to be appreciated that other arrangements of spacing elements 68 radially disposed about the axis A and coupled to the liner tube 64 may be achieved without departing from the nature of the invention.

In addition to spacing the liner tube 64 from the outer tube 60, the arrangement of the spacing elements 68 between the liner tube 64 and the outer tube 60 help to direct and control flow of the heated exhaust.

Referring to FIGS. 4A, 4B, and 4C, the outer tube 60 defines an interior surface 74 facing the liner tube 64. The liner tube 64 defines an exterior surface 76 facing the outer tube 60. In one embodiment, the spacing elements 68 are fixed to the liner tube 64 and abut the interior surface 74 of the outer tube 60. The outer tube 60 may define at least one indent on the interior surface 74 to receive the spacing elements 68 and axially locate the liner tube 64 to the outer tube 60. In another embodiment, the spacing elements 68 are fixed to the outer tube 60 and abut the exterior surface 76 of the liner tube 64. As illustrated in FIG. 4C, the liner tube 64 may define at least one indent 77 on the exterior surface 76 to receive the spacing elements 68, depressions 73 in this case and axially locate the outer tube 60 to the liner tube 64.

In one embodiment, the liner tube 64, the outer tube 60, and the spacing elements 68 are all comprised of a single metallic material. One distinct advantage of using a single material for each of the liner tube 64, the outer tube 60, and the spacing elements 68 is that properties of thermal expansion are consistent and any shrinking or expanding will be comparable between the liner tube 64, the outer tube 60, and the spacing elements 68. In one embodiment, the metallic material is one of titanium stabilized aluminized steel, aluminized steel, alumitherm steel, hot rolled steel, and stainless steel. In other embodiments the liner tube 64, the outer tube 60, and the spacing element 68 are comprised of any combination of materials suitable for use in radiant heating. Each of the liner tube 64, the outer tube 60, and the spacing elements 68 may be black coated, uncoated, or otherwise coated to imbue specific properties of radiation generally known in the art to the radiant heating assembly.

In one embodiment shown in FIGS. 4A, 4B and 4C, the outer tube 60 is disposed along an axis A and the spacing elements 68 concentrically aligns the liner tube 64 along the axis A.

In one embodiment, the exterior surface 76 of the liner tube 64 is further defined as a first surface 76 and the outer tube 60 defines a second surface 78 facing away from the liner tube 64. The first surface 76 has a first surface temperature and the second surface 78 has a second surface temperature. During operation of the radiant heating assembly 20, the first surface temperature is greater than the second surface temperature.

In one embodiment, the liner tube 64 is removable from the outer tube 60 and the radiant heating assembly 20 functions as a conventional radiant heating assembly 20 with an increased second surface 78 temperature.

In an alternative embodiment of the radiant heating assembly 20 as illustrated in FIGS. 6, 7, and 8, the radiant heating assembly 20 includes a housing 22 and an elongated heat exchanger 30 or burner tube in what is generally known in the art as a brooder 80.

In another embodiment illustrated in FIGS. 9A and 9B, the elongated heat exchanger 30 has a U-shape. As shown in a cross-section of the elongated heat exchanger 30 in FIG. 9B, the elongated heat exchanger 30 includes the liner tube 64, outer tube 60, and spacing element 68 similarly to the embodiments discussed above.

In another embodiment illustrated in FIGS. 10-11B, the radiant heating assembly 20 includes a temperature limiting device 82. The temperature limiting device 82 is coupled to the elongated heat exchanger 30 and includes a tube 84 and a temperature limit switch 86 coupled to the tube 84.

The tube 84 is coupled to the elongated heat exchanger 30 along the length of the elongated heat exchanger 30. The tube 84 defines an exterior surface 88 and an interior surface 90. The interior surface 90 defines a tube interior 92 in fluid communication with the elongated heat exchanger 30.

The temperature limit switch 86 is coupled to the exterior surface 88. As shown in FIGS. 11A and 11B, the temperature limit switch 86 is in electrical communication with the controller 50 and a power source 94. The power source 94 may be a 24 Volt power source. The temperature limit switch 86 is operable between a first state 96 and a second state 98. In the first state (FIG. 11A), the temperature limit switch 86 permits the controller 50 to receive power. In the second state 98 (FIG. 11B), the temperature limit switch 86 prohibits the controller 50 from receiving power. The temperature limit switch 86 is in the first state 96 when temperature of the exterior surface 88 of the tube 84 is at or below a predetermined temperature. The temperature limit switch 86 is in the second state 98 when temperature of the exterior surface 88 temperature of the tube 84 is above the predetermined temperature.

The temperature limit switch 86 is schematically shown in FIGS. 11A and 11B. The temperature limit switch 86 may be any temperature limit switch 86 generally known in the art as long as the controller 50 receives power from the power source 94 in the first state 96 and the controller 50 is prohibited from receiving power from the power source 94 in the second state 98. In one embodiment, the temperature limit switch 86 is a gauge that trips into the second state 98 when temperature of the exterior surface 88 exceeds the predetermined temperature. It is to be appreciated that the predetermined temperature may be any temperature selected prior to operation of the radiant heating assembly 20.

As illustrated in FIG. 11B, when the temperature limit switch 86 is in the second state 98 and the controller 50 does not receive power, the controller 50 restricts the burner 24 from receiving the air and fuel and combustion of the air and fuel ceases.

The controller 50 may be configured to prevent the burner 24 from receiving the fuel by modulating the fuel valve 36 to reduce the input rate to zero and close the fuel valve 36 completely when the controller 50 does not receive power. The controller 50 may prevent combustion of the air and fuel mixture in some other manner generally known in the art.

The controller 50 may be configured to open the fuel valve 36 and re-ignite the burner 24 when the temperature limit switch 86 returns to the first state 96.

In one embodiment illustrated in FIGS. 12A and 12B, the elongated heat exchanger 30 defines a temperature profile along the length of the elongated heat exchanger 30. The temperature limiting device 86 is coupled to the elongated heat exchanger 30 at a predetermined location. The predetermined location is located at a distance from the burner 24 where temperature of the exterior surface 88 of the tube 84 is highest relative to the temperature profile. The location on the elongated heat exchanger 30 with the highest temperature relative to the temperature profile is known as a “hot spot”. The distance of the hot spot from the burner 24 may be unique to individual radiant heating assemblies 20 as a result of any one or more of different lengths of heat exchangers 30, different specifications for burners 24, or other modifications between radiant heating assemblies 20. The location of the hot spot is determined during manufacture of the radiant heating assembly 20 and the temperature limiting device 86 is fixed at the hot spot. As such, the distance the temperature limiting device 86 is located from the burner 24 may change to accommodate the change in location of the hot spot.

As illustrated in FIG. 12A, the temperature limiting device 86 and hot spot (not shown) are located at a first distance 100 from the burner 24.

As illustrated in FIG. 12B, the temperature limiting device 86 and hot spot (not shown) are located at a second distance 102 from the burner 24, different from the first distance 100.

The invention may be used with anything from the most basic burner tube or heat exchanger connected to an on/off radiant heater to the most complex functionality of burner heat exchange unit with multiple or varied modulation, and have advantages in whatever configuration it is used. It may also be customized for specific applications.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications, variations, and combinations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described. 

What is claimed:
 1. A radiant heating assembly comprising: a burner for receiving air and fuel, and for combustion and emitting heated exhaust; and an elongated heat exchanger in fluid communication with said burner defining a first end, a second end and a length extending between said first and second ends, said elongated heat exchanger comprising: an outer tube disposed along at least a portion of said length and defining an interior; a liner tube disposed within said interior along at least a portion of said length and defining an inner chamber for receiving the heated exhaust from the burner; and at least one spacing element coupled to one of said liner tube and said outer tube and engaged with the other of said liner tube and said outer tube for spacing said liner tube from said outer tube along at least a portion of said length.
 2. A radiant heating assembly in accordance with claim 1, wherein said at least one spacing element is fixed to said liner tube.
 3. A radiant heating assembly in accordance with claim 2, wherein said outer tube defines an indent for receiving said at least one spacing element for locating said liner tube to said outer tube.
 4. A radiant heating assembly in accordance with claim 1, wherein said spacing element is a depression integrally formed with said liner tube.
 5. A radiant heating assembly in accordance with claim 1, wherein said outer tube is disposed along an axis and said at least one spacing element concentrically aligns said liner tube along said axis.
 6. A radiant heating assembly in accordance with claim 1, wherein said liner tube and said outer tube are comprised of a single metallic material.
 7. A radiant heating assembly in accordance with claim 6, wherein said material is alloy steel.
 8. A radiant heating assembly in accordance with claim 1, wherein said liner tube defines a first surface facing said outer tube and said outer tube defines a second surface facing away from said liner tube, said first surface having a first surface temperature and said second surface having a second surface temperature lower than said first surface temperature.
 9. A radiant heating assembly in accordance with claim 1, further including a plurality of spacing elements.
 10. A radiant heating assembly in accordance with claim 9, wherein said plurality of spacing elements are radially disposed about and coupled to said liner tube.
 11. A radiant heating assembly in accordance with claim 10, wherein said plurality of spacing elements define angles between adjacent spacing elements, with said axis being a vertex for each angle, said plurality of spacing elements are radially disposed about said liner tube such that angles between said plurality of spacing elements are equal.
 12. A radiant heating assembly in accordance with claim 10, wherein said plurality of spacing elements define angles between adjacent spacing elements, with said axis being a vertex for each angle, said plurality of spacing elements are radially disposed about said liner tube such that angles between said plurality of spacing elements are unequal.
 13. A radiant heating assembly in accordance with claim 10, wherein said plurality of spacing elements are disposed about said liner tube such that said spacing elements form a spiral about said liner tube along at least a portion of said length.
 14. A radiant heating assembly in accordance with claim 1, further including a fuel valve for providing the fuel to said burner.
 15. A radiant heating assembly in accordance with claim 14, further including a blower for providing the air to said burner.
 16. A radiant heating assembly in accordance with claim 15, further including a controller configured to control an amount of the air and the fuel provided to said burner.
 17. A radiant heating assembly in accordance with claim 1, wherein said liner tube and said outer tube comprise a U-shape.
 18. An inner tube assembly for a radiant heating assembly, with the radiant heating assembly comprising a burner for receiving air and fuel, and for combustion and emitting heated exhaust, and comprising an elongated heat exchanger in fluid communication with the burner for receiving the heated exhaust from the burner, with the elongated heat exchanger comprising an outer tube defining an interior comprising: a liner tube disposed within the interior, and said liner tube defining an inner chamber in fluid communication with the interior for receiving the heated exhaust from the burner; and at least one spacing element coupled to said liner tube for spacing said liner tube from the outer tube, directing the heated exhaust within the interior, and reducing surface temperature of the elongated heat exchanger.
 19. A radiant heating assembly comprising: a burner for receiving air and fuel, and for combustion and emitting heated exhaust; an elongated heat exchanger in fluid communication with said burner defining a first end and a second end and a length between said first and second ends; a controller configured to control the amount of the air and the fuel provided to said burner; and a temperature limiting device coupled to said elongated heat exchanger comprising: a tube having an exterior surface and an interior surface, with said interior surface defining a tube interior in fluid communication with said elongated heat exchanger, and with said tube coupled to said elongated heat exchanger along said length; and a temperature limit switch coupled to said exterior surface of said tube, with said temperature limit switch being operable between a first state when temperature of said exterior surface is at or below a predetermined temperature and a second state, different from said first state, when said temperature of said exterior surface is above said predetermined temperature.
 20. A radiant heating assembly in accordance with claim 19, wherein said temperature limit switch is in electrical communication with a power source and said controller, with said controller receiving power from said power source when said temperature limit switch is in said first state for allowing said burner to receive air and fuel, and with said temperature limit switch prohibiting said controller from receiving power when said temperature limit switch is in said second state for restricting said burner from receiving the air and fuel.
 21. A radiant heating assembly in accordance with claim 20, wherein said elongated heat exchanger defines a temperature profile along said length of said elongated heat exchanger, with said temperature limiting device coupled to said elongated heat exchanger at a predetermined location, and wherein said predetermined location is located along said length at a distance from said burner where said exterior surface temperature is highest with respect to said temperature profile.
 22. A temperature limiting device for a radiant heating assembly, the radiant heating assembly comprising a burner for receiving and combusting air and fuel and for emitting heated exhaust, the radiant heating assembly comprising an elongated heat exchanger in fluid communication with the burner for receiving the heated exhaust from the burner, and a controller configured to control the amount of the air and the fuel provided to the burner, the temperature limiting device comprising: a tube defining an exterior surface and an interior surface, with said interior surface defining a tube interior in fluid communication with and coupled to the elongated heat exchanger; a temperature limit switch coupled to said exterior surface of said tube, with said temperature limit switch being operable between a first state when temperature of said exterior surface is at or below a predetermined temperature and a second state, different from said first state, when said temperature of said exterior surface is above said predetermined temperature.
 23. A temperature limiting device in accordance with claim 22, wherein said temperature limit switch is in electrical communication with a power source and the controller, with the controller receiving power from said power source when said temperature limit switch is in said first state for allowing the burner to receive air and fuel, and with said temperature limit switch prohibiting the controller from receiving power when said temperature limit switch is in said second state for restricting the burner to receive the air and fuel. 